In a bizarre decision presumably made to reduce server overload fight credit card fraud, Blizzard said last night that new Diablo III players may not be able to play the entire game. Here's what Blizzard Support Forum Agent Medearn says:

As of patch 1.0.3, when purchasing a digital version of Diablo III through the online store or your Battle.net Account, players are restricted to the Starter Edition for the first 72 hours (sometimes less). Players on Starter Editions have the following restrictions:

Act I up to the Skeleton King is available

Level 13 cap

Matchmaking available only with other Starter Edition players

No Auction House access (Real Money or Gold)

Global Play is not available. Players attempting to connect to Diablo III Starter Edition in a region other than their Battle.net Account's home region will receive Error 12. See the Global Play support article for more information.

Outside of the issue that we fixed, digital purchases do require a review period before they kick over from Starter to Full editions. We apologize for the inconvenience, but it is a necessary step to combat fraud and other malicious activities that can weaken everyone's play experience.

The delay is no longer than three days, and is often much quicker than that. Hang tight. :)

Perhaps this is related to the bug caused by patch 1.0.3 that would block players from gaining experience points and level-cap their followers at 13, which Blizzard has since said was fixed.